Solar Builder

SEP-OCT 2018

Solar Builder focuses on the installation/construction of solar PV systems. We cover the latest PV technology (modules, mounting, inverters, storage, BOS) and equip installers/contractors with tips and tools to make informed purchasing decisions.

Issue link: http://digital.solarbuildermag.com/i/1019375

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16 S E P T E M B E R / O C TO B E R 2 0 1 8 MOUNTING NEW IN When augers, ground screws make economic sense for solar contractors By Cliff Schrock Market driver T he use of augers and ground screws has been of interest in mounting solar systems for some time, and for the right size job, they offer smaller solar contractors an opportunity to grow their business. Small site factors For one, with smaller PV systems, one may not need to spend money on a soil engineering analysis and the cost to permit the design separately. The typical soil type in an area may be known from experience. Perhaps local experience with other construction such as a home foundation or a water line installation can provide clues to the soil type. A method used by some contractors is to use a ham- mer drill and ground rod available from an electric supply store and see how easily the rod can be driven into the earth. If the rod hits solid rock 6 inches below the surface, or if the rod is very hard to drive, this could either disqualify the use of ground driven foundations, or in some cases lead to using ground screws rather than augers. Additionally, many counties and states have published maps showing the soil types for many locations. Other sources of data are well sites where there is often a record by the foot of the surface to depths much greater than one would drive a ground- mount. Selecting a ground-mount Once a determination has been made as to the type of soil at a site, the installer should select a ground mount to use at a site. If the soil type is not heavily compacted and not rocky, one can consider the use of augers. Most typically, a ground auger driven 7 to 10 ft. will suffice for most 3- and 4-row landscape arrays. If the ground is compacted, made up of heavy clay, or has small rocks within the first 10 ft., then a ground screw would probably be a better choice. Ground screws offer lower torque when driving them into the soil and are less likely to break in harder ground. However, in soft, loamy soils a ground screw will not provide big pullout values compared to an auger.

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